The genetics and ecology of social interactions

The evolution of any trait depends on genetics and ecology. Social traits are particularly interesting with respect to both factors. The inheritance of social traits can be complicated by indirect genetic effects that occur whenever the phenotype of one individual depends, at least in part, on the genotypes of its social partners. The ecology of social interactions depends on how individuals are distributed with respect to one another and their resources. Individuals may be distributed such that they encounter one another at random or such that they tend to encounter mostly relatives or such that they avoid interactions with other conspecifics all together. This distribution affects the selective pressures on social interactions. Here I present theoretical and empirical work related to these ideas.; A theoretical model presented in Chapter 2 shows how the two types of recognition errors associated with kin recognition differentially affect the evolution of altruism. In Chapter 3, indirect genetics effects theory is extended to include population structure and non-linear social effects. The remaining research chapters focus on empirical work relating to maternal care in the burrower bug, Sehirus cinctus. Potential costs are demonstrated for both egg guarding and maternal provisioning, though the cost of provisioning appears to be quite small. Experimental evidence indicates that offspring are able to elicit provisioning and are genetically variable in the ability to do so (i.e., an indirect genetic effect). Further, the results suggest that offspring elicitation is negatively correlated with maternal provisioning as predicted by maternal-offspring coadaptation theory. Finally, field and laboratory results are presented to show that social structure in this system may extend beyond the family unit. Lay sites in the field are aggregated and neighbors are unrelated. In addition, it is shown that offspring sometimes leave their hatch site to form multifamily groups. Thus, both mothers and offspring contribute to the social context in which offspring develop. A complete understanding of maternal-offspring interactions requires that these behaviors be interpreted within this broader social context.